Swash plate-type variable displacement compressors

ABSTRACT

A swash plate-type, variable displacement compressor includes a front housing, a cylinder block, a rear housing, and a drive shaft rotatably supported by the front housing and by the cylinder block. The compressor also includes a rotor fixed to the drive shaft, such that the rotor and the drive shaft rotate together, and a plurality of pistons, each of which is slidably positioned within a corresponding cylinder bore. The compressor further includes a swash plate having a penetration hole formed through a center portion of the swash plate. Moreover, the drive shaft extends through the penetration hole and the swash plate is connected to the pistons via a pair of shoes. The compressor also includes a hinge mechanism which connects the rotor to the swash plate. The hinge mechanism includes a single rotor arm having an oblong hole formed therethrough, and a single swash plate arm having a pin portion extending therefrom, such that the pin portion slidably engages an inner wall of the oblong hole. When a mechanical load of the compressor is greater than a predetermined mechanical load, a resultant force of the mechanical load is located at a point along a first portion of a force line, and an area of engagement between a surface of the pin portion and the inner wall of the oblong hole includes the first portion of the force line.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates generally to swash plate-type, variable displacement compressors for use in an air conditioning system of a vehicle. More particularly, the invention relates to swash plate-type, variable displacement compressors having a hinge coupling mechanism positioned between a rotor and a swash plate.

[0003] 2. Description of Related Art

[0004] Referring to FIG. 1, a known, swash plate-type, variable displacement compressor (A) for use in an air conditioning system of a vehicle (not shown), such as the known compressor described in Japanese Patent Publication No. 2001-200783, is depicted. Compressor (A) includes a front housing 7, a cylinder block 6, a rear housing 8, and a drive shaft 1. Front housing 7, cylinder block 6, and rear housing 8 may be fixably attached to each other by a plurality of bolts 15. Drive shaft 1 may pass through the center of front housing 7 and the center of cylinder block 6. Drive shaft 1 also may be rotatably supported by front housing 7 and by cylinder block 6 via a pair of bearings 11 and 12 mounted in front housing 7 and cylinder block 6, respectively. A plurality of cylinder bores 6a may be formed within cylinder block 6 and also may be positioned equiangularly around an axis of rotation 20 of drive shaft 1. Moreover, a piston 5 may be slidably positioned within each cylinder bore 6 a, such that pistons 5 reciprocate on axes parallel to axis 20 of drive shaft 1.

[0005] Compressor (A) also includes a rotor 2, a crank chamber 30, and a swash plate 3. Specifically, rotor 2 is fixed to drive shaft 1, such that drive shaft 1 and rotor 2 rotate together. Crank chamber 30 is formed between front housing 7 and cylinder block 6, and swash plate 3 may be positioned inside crank chamber 30. Swash plate 3 may be slidably connected to each piston 5 via a pair of shoes 4 positioned between swash plate 3 and each of pistons 5. Swash plate 3 may include a penetration hole 3 c formed therethrough at a center portion of swash plate 3, and drive shaft 1 may extend through penetration hole 3 c. Rotor 2 includes a pair of rotor arms 2 a and an oblong hole 2 b formed through each of rotor arms 2 a, and swash plate 3 further includes a pair of swash plate arms 3 a and a pin 3 b extending from each of swash plate arms 3 a. A hinge mechanism 9 includes rotor arms 2 a, swash plate arms 3 a, oblong holes 2 b, and pins 3 b, and rotor 2 may be connected to swash plate 3 by hinge mechanism 9. Specifically, a first of pins 3 b may be inserted into and may slidably engage an inner wall of a first of oblong holes 2 b, and a second of pins 3 b may be inserted into and may slidably engage an inner wall of a second of oblong holes 2 b. Moreover, because each of pins 3 b may move within their corresponding oblong hole 2 b, the tilt angle of swash plate 3 may be varied with respect to drive shaft 1, such that the fluid displacement of compressor (A) also may be varied.

[0006] Compressor (A) also may include an electromagnetic clutch (not shown). When the electromagnetic clutch is activated, a driving force from an external driving source (not shown) is transmitted to drive shaft 1, such that drive shaft 1, rotor 2, and swash plate 3 rotate substantially simultaneously about axis 20 of drive shaft 1. Moreover, swash plate 3 also moves back and forth in a wobbling motion, such that only movement in a direction parallel to axis 20 of drive shaft 1 is transferred from swash plate 3 to pistons 5. Consequently, each piston 5 reciprocates within its corresponding cylinder bore 6 a and compresses a fluid, eg., a refrigerant, within a compression chamber 50 formed by a top portion of piston 5, the walls of cylinder bore 6 a, and a valve plate 40.

[0007] Referring to FIG. 2, a partial, cross-sectional view of compressor (A) taken along a line II-II in a direction (Z) is depicted. A plane II includes a first axis (x) and a second axis (y), in which second axis (y) includes axis 20 of drive shaft 1 and first axis (x) is perpendicular to second axis (y). Plane II also includes an upper dead center portion (P) of swash plate 3. Moreover, in compressor (A), cylinder bores 6 a comprise a first cylinder bore 6 a 1, a second cylinder bore 6 a 2, a third cylinder bore 6 a 3, a fourth cylinder bore 6 a 4, a fifth cylinder bore 6 a 5, and a sixth cylinder bore 6 a 6. When pistons 5 reciprocate within corresponding cylinder bores 6 a 1-6 a 6, respectively, each of pistons 5 apply an anti-compressive force on swash plate 3. Specifically, pistons 5 apply anti-compressive forces (f₁), (f₂), (f₃), (f₄), (f₅), and (f₆) on swash plate 3 at positions (x1, y1), (x2, y2), (x3, y3) (x4, y4), (x5, y5), and (x6, y6), respectively. Japanese Patent Publication No. HEI 8-49653 describes an exemplary change in force (f_(i)) relative to a piston stroke phase in compressor (A). As shown in FIG. 2, the resultant anti-compressive force (F) acts on hinge mechanism 9 and is shown at a representative position (R). Resultant force (F) and position (R) may be represented by Cartesian coordinates (X_(R), Y_(R)), such that the following formulas are satisfied:

X_(R)=(Σf_(i)*x_(i))/Σf_(i;)   (1)

Y_(R)=(Σf₁* y_(i))/Σf_(i); and   (2)

F=Σf_(i), in which (i) equals 1-6.   (3)

[0008] The mechanical load on compressor (A) depends on a difference between a discharge pressure of the refrigerant and a suction pressure of the refrigerant. Moreover, the discharge pressure of the refrigerant and the suction pressure of the refrigerant depend on a thermal load on the air conditioning system, and the thermal load on the air conditioning system depends on a temperature of the vehicle. As such, the mechanical load on compressor (A) continuously changes. When the mechanical load on compressor (A) changes, the magnitude of resultant force (F) acting on hinge mechanism 9 via swash plate 3 also changes. Specifically, when the mechanical load on compressor (A) decreases, result force (F) also decreases, and position (R) moves towards axis 20 of drive shaft 1. Similarly, when the mechanical load on compressor (A) increases, result force (F) also increases, and position (R) moves away from axis 20 of drive shaft 1. Thus, when the mechanical load on compressor (A) changes between a minimum mechanical load and a maximum mechanical load, position (R) at which resultant force (F) acts on swash plate 3 moves from a first portion (t₁) of a force line (t) to a second portion (t₂) of force line (t). Second portion (t₂) of force line (t) is located further from axis 20 of drive shaft 1 than first portion (t₁) of force line (t), and force line (t) is defined as a set of positions (R) in plane II at which resultant force (F) may be located. According to a computer simulation, force line (t) is a substantially straight line and a first end of first portion (t₁) of force line (t) intersects axis (y) to form an acute angle θ having a value between about 15° and about 25°. Nevertheless, it will be understood by those of ordinary skill in the art that the value of angle θ depends on the number of cylinder bores 6 a formed within cylinder block 6 and the properties of the refrigerant used in the compressor.

[0009] When the mechanical load on compressor (A) is less than a predetermined mechanical load, position (R), at which resultant force (F) acts on swash plate 3, is located along first portion (t₁) of force line (t). Moreover, the resultant force (F) acts on hinge mechanism 9 via swash plate 3 by each of the pair of rotor arms 2 a. Specifically, resultant force (F) acts on hinge mechanism 9 by a first rotor arm 2 a ₁ and a second rotor arm 2 a ₂. Similarly, when the mechanical load on compressor (A) is greater than the predetermined mechanical load, position (R) at which resultant force (F) acts on swash plate 3, is located along second portion (t₂) of force line (t). Nevertheless, the resultant force (F) acts on hinge mechanism 9 via swash plate 3 substantially by first rotor arm 2 a ₁. Consequently, when the mechanical load on compressor (A) is at a maximum, the maximum resultant force (F) acts on hinge mechanism 9 substantially by one of rotor arms 2 a.

SUMMARY OF THE INVENTION

[0010] Therefore, a need has arisen for swash plate-type, variable displacement compressors which overcome these and other short comings of the related art. A technical advantage of the present invention is that the number of parts may be reduced without decreasing performance of the compressors. Specifically, a rotor may comprise a single rotor arm having an oblong hole formed therethrough, and a swash plate may comprise a single swash plate arm having a pin extending therefrom. Consequently, another technical advantage of the present invention is that the manufacturing cost of each of the compressors may be reduced without decreasing performance of the compressors.

[0011] According to an embodiment of the present invention, a swash plate-type, variable displacement compressor is described. The compressor comprises a front housing, a cylinder block, a rear housing, and a drive shaft rotatably supported by the front housing and by the cylinder block. A plurality of cylinder bores are formed within the cylinder block. The compressor also comprises a rotor fixed to the drive shaft, such that the rotor and the drive shaft rotate together, and a plurality of pistons, each of which is slidably positioned within a corresponding cylinder bore. The compressor further comprises a swash plate having a penetration hole formed through a center portion of the swash plate, such that the drive shaft extends through the penetration hole. Moreover, the swash plate is connected to each of the pistons by a pair of shoes. The compressor also comprises a hinge mechanism which connects the rotor to the swash plate, such that a tilt angle of the swash plate varies with respect to an axis of rotation of the drive shaft. The hinge mechanism comprises a single rotor arm having an oblong hole formed therethrough, and a single swash plate arm having a pin portion extending therefrom, such that the pin portion slidably engages an inner wall of the oblong hole. When a mechanical load of the compressor is greater than a predetermined mechanical load, a resultant force of the mechanical load is located at a point along a first portion of a force line, and an area of engagement between a surface of the pin portion and the inner wall of the oblong hole comprises the first portion of the force line.

[0012] Other objects, features, and advantages will be apparent to persons of ordinary skill in the art in view of the following detailed description of the invention and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] For a more complete understanding of the present invention, the needs satisfied thereby, and the features and advantages thereof, reference now is made to the following descriptions taken in connection with the accompanying drawings.

[0014]FIG. 1 is a cross-sectional view of a known, swash plate-type, variable displacement compressor.

[0015]FIG. 2 is a partial, cross-sectional view of the compressor of FIG. 1 taken along a line II-II in a direction (Z).

[0016]FIG. 3 is a cross-sectional view of a swash plate-type, variable displacement compressor according to an embodiment of the present invention.

[0017]FIG. 4 is a partial, cross-sectional view of the compressor of FIG. 3 taken along a line IV-IV in a direction (Z).

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0018] Preferred embodiments of the present invention and their advantages may be more readily understood by referring to FIGS. 3 and 4, like numerals being used for like corresponding parts in the various drawings.

[0019] Referring to FIG. 3 a swash plate-type, variable displacement compressor (A′) for use in an air conditioning system of a vehicle (not shown) according to an embodiment of the present invention is depicted. Compressor (A′) may comprise a front housing 7, a cylinder block 6, a rear housing 8, and a drive shaft 1. Front housing 7, cylinder block 6, and rear housing 8 may be fixably attached by a plurality of bolts 15. Drive shaft 1 may pass through the center of front housing 7 and the center of cylinder block 6. Drive shaft 1 also may be rotatably supported by front housing 7 and by cylinder block 6 via a pair of bearing 11 and 12 mounted in front housing 7 and cylinder block 6, respectively. A plurality of cylinder bores 6 a may be formed within cylinder block 6 and also may be positioned equiangularly around an axis of rotation 20 of drive shaft 1. Moreover, a piston 5 may be slidably positioned within each cylinder bore 6 a, such that pistons 5 reciprocate along axes parallel to an axis 20 of drive shaft 1.

[0020] Compressor (A′) also may comprise a rotor 2, a crank chamber 30, and a swash plate 3. Specifically, rotor 2 is fixed to drive shaft 1, such that drive shaft 1 and rotor 2 rotate together. Crank chamber 30 is formed between front housing 7 and cylinder block 6, and swash plate 3 may be positioned inside crank chamber 30. Swash plate 3 may be slidably connected to each piston 5 via a pair of shoes 4 positioned between swash plate 3 and each of pistons 5. Swash plate 3 may include a penetration hole 3c formed therethrough at a center portion of swash plate 3, and drive shaft 1 may extend through penetration hole 3 c. Rotor 2 may comprise a single rotor arm 2 a′ and an oblong hole 2 b′ formed through rotor arm 2 a′, and swash plate 3 further may comprise a single swash plate arm 3 a′ and a pin 3 b′ extending from swash plate arm 3 a′. A hinge mechanism 9′ may comprise rotor arm 2 a′, swash plate arm 3 a′, oblong hole 2 b′, and pin 3 b′, and rotor 2 may be connected to swash plate 3 by hinge mechanism 9′. Specifically, pin 3 b′ may be inserted into and may slidably engage an inner wall of oblong hole 2 b′. Moreover, because pin 3 b′ may move within oblong hole 2 b′, the tilt angle of swash plate 3 may be varied with respect to drive shaft 1, such that the fluid displacement of compressor (A′) also may be varied.

[0021] Compressor (A′) also may comprise an electromagnetic clutch (not shown). When the electromagnetic clutch is activated, an external driving force from an external driving source (not shown) is transmitted to drive shaft 1, such that drive shaft 1, rotor 2, and swash plate 3 rotate substantially simultaneously about axis 20 of drive shaft 1. Moreover, swash plate 3 also moves back and forth in a wobbling motion, such that only movement in a direction parallel to axis 20 of drive shaft 1 is transferred from swash plate 3 to pistons 5. Consequently, each piston 5 reciprocates within its corresponding cylinder bore 6 a and compresses a fluid, eg., a refrigerant, within a compression chamber 50 formed by a top portion of piston 5, the walls of cylinder bore 6 a, and a valve plate 40.

[0022] Referring to FIG. 4, a partial, cross-sectional view of compressor (A′) taken along a line IV-IV in a direction (Z) is depicted. A plane II includes a first axis (x) and a second axis (y), in which second axis (y) includes axis 20 of drive shaft 1 and first axis (x) is perpendicular to axis (y). Plane II also includes an upper dead center portion (P) of swash plate 3. Moreover, in compressor (A′), cylinder bores 6 a comprise a first cylinder bore 6 a 1, a second cylinder bore 6 a 2, a third cylinder bore 6 a 3, a fourth cylinder bore 6 a 4, a fifth cylinder bore 6 a 5, and a sixth cylinder bore 6 a 6. When pistons 5 reciprocate within corresponding cylinder bores 6 a 1-6 a 6, respectively, each of pistons 5 apply an anti-compressive force on swash plate 3. Specifically, pistons 5 apply anti-compressive forces (f₁), (f₂), (f₃), (f₄), (f₅), and (f₆) on swash plate 3 at positions (x1, y1), (x2, y2), (x3, y3) (x4, y4), (x5, y5), and (x6, y6), respectively. Referring to FIG. 4, resultant anti-compressive force (F) acts on hinge mechanism 9′ and is shown at a representative position (R). Resultant force (F) and position (R) may be represented by Cartesian coordinates (X_(R), Y_(R)), such that the following formulas are satisfied:

X_(R)=(Σf_(i)*x_(i))/Σf_(i;)   (1)

Y_(R)=(Σf_(i)*y_(i))/Σf_(i); and   (2)

F=Σf₁, in which (i) equals 1, 2, 3, 4, 5, and 6.   (3)

[0023] The mechanical load on compressor (A′) depends on a difference between a discharge pressure of the refrigerant and a suction pressure of the refrigerant. Moreover, the discharge pressure of the refrigerant and the suction pressure of the refrigerant depend on a thermal load on the air conditioning system, and the thermal load on the air conditioning system depends on a temperature of the vehicle. As such, the mechanical load on compressor (A′) continuously changes. When the mechanical load on compressor (A′) changes, the magnitude of resultant force (F) acting on hinge mechanism 9′ via swash plate 3 also changes. Specifically, when the mechanical load on compressor (A′) decreases, resultant force (F) also decreases, and position (R) moves towards axis 20 of drive shaft 1. Similarly, when the mechanical load on compressor (A′) increases, resultant force (F) also increases, and position (R) moves away from axis 20 of drive shaft 1. Thus, when the mechanical load on compressor (A′) changes between a minimum mechanical load and a maximum mechanical load, position (R) at which resultant force (F) acts on swash plate 3 moves from a first portion (t₁) of a force line (t) to a second portion (t₂) of force line (t). Second portion (t₂) of force line (t) is located further from axis 20 of drive shaft 1 than first portion (t₁) of force line (t), and force line (t) is defined as a set of positions (R) in plane II at which resultant force (F) may be located. According to a computer simulation, force line (t) is a substantially straight line and a first end of first portion (t₁) of force line (t) intersects axis (y) to form an acute angle θ having a value between about 15° and about 25°. Nevertheless, it will be understood by those of ordinary skill in the art that the value of angle θ depends on the number of cylinder bores 6 a formed within cylinder block 6 and the properties of the refrigerant used in the compressor.

[0024] When the mechanical load on compressor (A′) is less than a predetermined mechanical load, position (R) at which resultant force (F) acts on swash plate 3 is located along first portion (t₁) of force line (t). Moreover, the resultant force (F) acts on hinge mechanism 9′ via swash plate 3 by rotor arm 2 a′. Similarly, when the mechanical load on compressor (A′) is greater than the predetermined mechanical load, position (R) at which resultant force (F) acts on swash plate 3 is located along second portion (t₂) of force line (t). Further, the resultant force (F) acts on hinge mechanism 9′ via swash plate 3 by rotor arm 2 a′. A region (S) is defined as an area of engagement between a surface of pin 3 b′ and the inner wall of oblong hole 2 b′ in plane II. Hinge mechanism 9′ may support a greater resultant force (F) when position (R) of resultant force (F) is inside region (S) than when position (R) is outside region (S). In one embodiment, a size of hinge mechanism 9′ may be selected, such that region (S) substantially or entirely includes portion (t₂) of force line (t). When the mechanical load on compressor (A′) is less than the predetermined mechanical load, position (R) of resultant force (F) is outside region (S). Nevertheless, because position (R) of resultant force (F) lies outside region (S) only when the mechanical load of compressor (A′) is less than the predetermined mechanical load, the mechanical load of compressor (A′) may be supported by a single rotor arm and a single swash plate arm, without degrading compressor performance.

[0025] While the invention has been described in connection with preferred embodiments, it will be understood by those skilled in the art that other variations and modifications of the preferred embodiments described above may be made without departing from the scope of the invention. Other embodiments will be apparent to those skilled in the art from a consideration of the specification or practice of the invention disclosed herein. It is intended that the specification and the described examples are considered as exemplary. 

What is claimed is:
 1. A swash plate-type, variable displacement compressor comprising: a front housing; a cylinder block, wherein a plurality of cylinder bores are formed within said cylinder block; a rear housing; a drive shaft rotatably supported by said front housing and by said cylinder block; a rotor fixed to said drive shaft, such that said rotor and said drive shaft rotate together; a plurality of pistons, each of which is slidably positioned within a corresponding cylinder bore; a swash plate having a penetration hole formed through a center portion of said swash plate, wherein said drive shaft extends through said penetration hole and said swash plate is connected to each of said pistons by a pair of shoes; and a hinge mechanism connecting said rotor to said swash plate, such that a tilt angle of said swash plate varies with respect to an axis of rotation of said drive shaft, wherein said hinge mechanism comprises: a single rotor arm having an oblong hole formed therethrough; and a single swash plate arm having a pin portion extending therefrom, wherein said pin portion slidably engages an inner wall of said oblong hole, and when a mechanical load of said compressor is greater than a predetermined mechanical load, a resultant force of said mechanical load is located at a point along a first portion of a force line, wherein an area of engagement between a surface of said pin portion and said inner wall of said oblong hole comprises said first portion of said force line.
 2. The compressor of claim 1, wherein when a mechanical load of said compressor is less than said predetermined mechanical load, said resultant force of said mechanical load is located at a point along a second portion of said force line.
 3. The compressor of claim 2, wherein said second portion of said force line is substantially outside said area of engagement between said surface of said pin portion and said inner wall of said oblong hole.
 4. The compressor of claim 2, wherein said second portion of said force line is entirely outside said area of engagement between said surface of said pin portion and said inner wall of said oblong hole. 